Timing drive tensioners are designed to control timing drive dynamic inputs transmitted through the chain and ultimately the tensioner arm/face. In order to achieve this control, tensioners are ‘tuned’ via mechanical, hydraulic or a combination of both methods. As the chain wears, a typical tensioner piston extends as designed to take up chain slack. Piston extension reduces mechanical bias spring force and can increase hydraulic leakage changing the tensioner tuning. This change in tuning during the life cycle of the tensioner can be compensated for by over-tensioning the tensioner when the tensioner is new to compensate for piston extension during the worn chain portion of the life cycle. Over-tensioning of the tensioner has an adverse effect on efficiency and system durability.
A necessary function of a tensioner is to extend to take up chain slack as the chain wears. In a conventional tensioner, chain take up increases compression spring length reducing chain preload requiring excessive preload at new chain conditions to compensate, which adversely effects efficiency and system durability.